Hi. I should mention from the start that this is a question about an engineering task, not a question about FreeBSD issue. I have a set of zvol clones that I redistribute over iSCSI. Several Windows VMs use these clones as disks via their embedded iSCSI initiators (each clone represents a disk with an NTFS partition, is imported as a "foreign" disk and functions just fine). From my opinion, they should not have any need to do additional writes on these clones (each VM should only read data, from my point of view). But zfs shows they do, and sometimes they write a lot of data, so clearly facts and expactations differ a lot - obviously I didn't take something into accounting. Is there any way to figure out what these writes are ? Because I cannot propose any simple enough method. Thanks. Eugene.
On 22/09/2016 13:56, Eugene M. Zheganin wrote:> Is there any way to figure out what these writes are ? Because I cannot > propose any simple enough method.Given you're using volumes for datasets where ZFS knows nothing about the contained filesystem structure, about the only way to proceed is via the windows site of things. You'ld need to somehow trap where windows issues a write and proceed from there. Ideally you could do something like snapshot NTFS, wait until windows has written something and then compare the snapshot with the live filesystem. Very cursory Googling suggests that Microsoft calls this sort of thing a 'shadow copy' Cheers, Matthew -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 931 bytes Desc: OpenPGP digital signature URL: <http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20160922/d2234c09/attachment.sig>
On Thu, Sep 22, 2016 at 04:56:53PM +0500, Eugene M. Zheganin wrote:> Hi. > > I should mention from the start that this is a question about an > engineering task, not a question about FreeBSD issue. > > I have a set of zvol clones that I redistribute over iSCSI. Several > Windows VMs use these clones as disks via their embedded iSCSI > initiators (each clone represents a disk with an NTFS partition, is > imported as a "foreign" disk and functions just fine). From my opinion, > they should not have any need to do additional writes on these clones > (each VM should only read data, from my point of view). But zfs shows > they do, and sometimes they write a lot of data, so clearly facts and > expactations differ a lot - obviously I didn't take something into > accounting.May be atime like on NTFS? http://serverfault.com/questions/33932/how-do-you-disable-the-last-accessed-attribute-on-ntfs-windows